The 802.11a physical layer may support wireless communication at rates of up to 54 Mbps in the 5 GHz band. The 802.11a 5 GHz band is divided into a lower band of 5.15-5.25 GHz, a middle band of 5.25-5.35 GHz, and an upper band of 5.725-5.825 GHz. Operating in any of the channels of the lower band can be considered operating in the lower band of 5.15-5.25 GHz. A dual band antenna refers generally to the 2.4 GHz band and the lower and middle 802.11a bands. A triband antenna refers generally to the 2.4 GHz band and all 802.11a bands.
Advantageous flexibility would be provided by a wireless node having an external, detachable antenna for 802.11a. For example, the antenna could be relocated in a better location. Various antennas could be used with the wireless node, such as an omnidirectional antenna or a directional antenna. Additionally, electronics could be separated from antenna.
However, government regulations can require that 802.11a lower band communications occur via an integral antenna. In particular, the Federal Communications Commission provides in Title 47 of the Code of Federal Regulations, section 15.407, that any unlicensed National Information Infrastructure device that operates in the 5.15-5.25 GHz band shall use a transmitting antenna that is an integral part of the device.
Thus, it would be desirable if a wireless node could have a detachable antenna and still comply with government rules on 802.11a lower band communications.